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Green Building Insulation

Green Insulator Resource

Sustainable building starts with reducing the heating and cooling loads of the home as much as possible and insulation is the key to energy conservation, a cornerstone of green building. Well-insulated houses not only save energy, thus lowering operating costs, but also keep people more comfortable.

Appropriate Type and Amount of Insulation

Because different types of insulation have different insulating values (R-values), what you choose determines how the house is framed and detailed on the outside. Your exact route will probably take a variety of factors into account:

the appropriate level of insulation for the region where you build. See a the climate zones around the country and their recommended insulation levels in Chapter 11 on Insulation in the Green from the Ground Up book for more details.

your experience with alternative building practices

the availability of different kinds of insulation

how much experience your insulation contractor has

the design of the house

local cost comparisons for different types of insulation

Green Insulator’s Transition Guide

Conduct a Home energy audit, how much insulation is there?

An audit will indicate how a house is performing and where it is loosing heat.

A blower door test and infrared camera will outline the problem areas.

Contact a licensed HERS energy auditor in your area, or look into become certified yourself

Seal all wall penetrations such as wires or pipes or electrical outlets

Even a small air leak can have a huge impact on heat loss over the life of the building

Use expansion foam

Canned expansion foam. Look for products that use HFC rather than HCFC or CFC as propellants.

Add additional insulation to the attic

An attic is a great place to pile on the insulation. A large quantity of a home’s heat is lost through the attic

Lay R-38 batts perpendicular to each other or blow at least 10 inches of cellulose in most climates.

Green from the Ground Up Best Practices

Treat insulation recommendations from the Department of Energy as minimums. Aim for insulation levels that are 50% better.

Use insulation that completely fills walls and ceiling cavities and reduces or eliminates air leaks – structural insulated panels, spray-in foam, or spray-in cellulose or fiberglass are the best products for this.

Avoid fiberglass batts if possible; if they must be used, make sure the installer knows what he’s doing. Supplement batts with a layer of rigid foam insulation on the exterior of the building.

Do not use light-gauge steel framing on exterior walls without a layer of exterior insulation to counteract thermal bridging.

When calculating the desired thermal performance of a wall or ceiling, don’t forget to include the effects of doors, windows, and other materials that penetrate the building envelope. In general, real performance will be lower than the nominal R-value of the insulation you’re using. Plan accordingly.

Don’t confuse a thermal barrier with an air barrier. One retards the flow of heat, the other prevents air infiltration and the migration of water vapor into wall and ceiling cavities. Both are important.